The trigonometric form of z is , where

1).If a > 0, then

2).If a < 0, then

The complex number is .

Compare the complex number with a + ib.

a = 2 and b = 0.

The absolute value of  z :

a = 2 < 0, so the angle is :

The trigonometric form is .

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The trigonometric form is .